Role of Rainfall in the Earth System
The atmosphere, oceans and biosphere of our planet are closely coupled components of the global environment, which is often called the Earth system. The unifying element of these large environmental systems is water. It is the active component of the atmosphere, it covers three quarters of the Earth's surface; and is the basis for all life on our planet. Water is essential to our continued existence.
Because of the unifying role of the global water cycle, studies of rainfall are essential for a deeper understanding of the Earth as a system. TRMM is studying these aspects of the Earth system:
Earth Science: Research in the Earth's system components can reveal the interaction of the ocean with the atmosphere, coupled with the many different life forms that make up the Earth's biosphere. Incorporating these interactions in Earth system models will test our understanding of the basic mechanisms, such as rainfall, and will improve simulations of future global trends.
Atmospheric Circulation: Rainfall releases tremendous amounts of latent heat that have enormous impact on weather and climate. Because we do not have adequate rain measurements, existing climate models do not accurately predict the amounts of heat being released. TRMM data will help climate modelers in remedying one of their most serious deficiencies by providing more accurate rain and heat information.
Ocean-Atmosphere Interaction: The ocean influences atmospheric dynamics through evaporation and heat transfer. Tropical clouds can act as a shield against solar radiation impinging on the sea surface. There is a close coupling between the development of large cloud systems and warmth of the sea surface. Interaction between ocean and atmosphere is vital in weather and climate on all scales.
The Biosphere: Tropical forests and their soils are a major source of many of the atmosphere's trace constituents. Together, forests and the atmosphere act as a single water and energy-regulating system. Water received as rainfall returns to the atmosphere through evaporation and transpiration.
The environment recycles a large portion of this returned water. During a rainstorm, clouds transport these atmospheric trace constituents into the free atmosphere while cleaner air flows down to the surface. This exchange reveals a direct link between tropical rainfall and the global cycles of carbon, nitrogen and sulfur, which are important in biological processes.